REPRODUCTIONRESEARCH Embryonic exposure to oestrogen causes eggshell thinning and altered shell gland carbonic anhydrase expression in the domestic hen C Berg, A Blomqvist1, L Holm1, I Brandt, B Brunstro¨m and Y Ridderstra˚le1 Department of Environmental Toxicology, Uppsala University, Norbyva¨gen 18 A, 753 36 Uppsala, Sweden and 1Department of Anatomy and Physiology, Swedish University of Agricultural Sciences, Box 7045, 750 07 Uppsala, Sweden Correspondence should be addressed to C Berg; Email:
[email protected] Abstract Eggshell thinning among wild birds has been an environmental concern for almost half a century. Although the mechanisms for contaminant-induced eggshell thinning are not fully understood, it is generally conceived to originate from exposure of the laying adult female. Here we show that eggshell thinning in the domestic hen is induced by embryonic exposure to the syn- thetic oestrogen ethynyloestradiol. Previously we reported that exposure of quail embryos to ethynyloestradiol caused histo- logical changes and disrupted localization of carbonic anhydrase in the shell gland in the adult birds, implying a functional disturbance in the shell gland. The objective of this study was to examine whether in ovo exposure to ethynyloestradiol can affect eggshell formation and quality in the domestic hen. When examined at 32 weeks of age, hens exposed to ethynyloestra- diol in ovo (20 ng/g egg) produced eggs with thinner eggshells and reduced strength (measured as resistance to deformation) compared with the controls. These changes remained 14 weeks later, confirming a persistent lesion. Ethynyloestradiol also caused a decrease in the number of shell gland capillaries and in the frequency of shell gland capillaries with carbonic anhy- drase activity.